The junipers are like a blank canvas, and you could create any shape you want with a little trimming and removal. You could change it into a half moon, kidney shape, uniform rectangle, or something more wild like a series of squares, lines or circles (I'm thinking Martha Schwartz here). You can also change it by adding trees and shrubs in specific locations, depends upon what kind of look you want.
For a natural look, add one conifer and three flowering shrubs/ornamental grasses at the top corner, one deciduous tree and three flowering shrubs/ornamental grasses at the opposite bottom corner, and one deciduous or conifer tree plus 5 flowering shrubs/ornamental grasses/ perennials somewhere towards the middle, but not perfectly centered. You may also want to trim/remove some junipers on the edges to make it more natural looking.
You might want to look through some landscaping books at the library to get ideas